Automatic cut-off device for fuel-oil burners



D. R. MARTIN AUTOMATIC CUT-OFF DEVICE FOR FUEL OIL BURNERS July 31, 1928.

Filed April 22, 1.926

I N VEN TOR. U/PAJ /2 MMT/M .fl TTORNEY.

Patented `luly 31, 1928.

UNITED STATES PATENT oFF1,cE.j

DORE R. MARTIN, OF DETROIT, MICHIGAN.

AUTOMATIC CUT-OFF DEVICE FOR FUEL-QILBURNERS.

Application med 'April 22, 192s. semi-N6. massa'.

This invention relates to automatic cut oft' devices for fuel oil burners and the object of the invention is to provide a device for stopping flow of fuel should the burner vfail to ignite. Y

This device is designed for use with the intermittent type of fuel oil burner in which the re turns on and off intermittently and is usually controlled by a thermostat for this purpose. i

Another object of the invention is to pro-Y the burner, the air under pressure being, utilized to actuate a means for breaking the circuitto the electric motor to stop the pump should the oil fail to ignite. A

These objects and the several novel features of the invention are hereinafter more fully described and claimed and the preferred form of construction by which thesel objects are attained is shown in the accom-y panying drawings in which# Fig. 1 is a section through an automatic cut ofl' device embodying` my invention.

Fig. 2 is a view of the electrically driven pumpand circuit therefor. c Y

The pump 1, shown in Fig. 2, is ofthe usual type having an air inlet pipe 2 and an air outlet pipe 3 through which air is discharged under pressure. The pump 1 is driven by an electric motor 4 which is pro vided with current through the two wires 5 and 6. Two switches 7 and Svare provided in the line 5 either one of which may be opened to break the motor circuit. The

switch 7 is preferably controlled by a ther-r mostat which controls the motor according to the temperature -of the housev being heated. The switch'S is shown more particula-rly in Fig. -1 and is-provided with a ,switch button 9 which .in the position shown in full 'lines in Fig. 1 is closed. The lpressure line 3, as shown in Fig. 1, leads to a nozzle 10 extending through the furnace wall 11 and through which a fuel oil and air mixture is sprayed into the interior of the furnace the fuel oil being fed to the mixing nozzle 10 lthrough the pipe 40. A pipe 12 leads from the pipe 3 to the housing 13 shown` in Fig. 1 and a member 14 is provided having a very small aperturey therethrough through which air under pressure may flow very slowly. An annularly corrugated sheet metal expanding element is provided in the housing 13 into which'the air under pressure is adapted to pass fromthe member 14 and this member 15 is closed atthe. end by a member 16 having a stem 17 passing through an apertured bracket 18 formed i integrally with the housing 13. A` coiled spring 19 is positioned between the stationary member 18 and the movable member 16 and a link 20 is pivotally connected to the stem 17. 'A second link21 is pivotally conif nected at one end to the link 2O and at the opposite end tothe actuating member 22 which also extends through an aperture in the stationary 'bracket 18. The 'actuating member 22 is provided withl an enlarged end 23 adapted to engage the switch button 9.

.l/Vhen the pump starts operating the airv under pressure flows through the `nozzle 10 where it is mixed with oil and discharged into the furnace- 11 and the air under pressure also flows slowly through the small aperture in the member 14 into the longitudinally yeXpandible element 15 which moves the stem 17. to the .left of Fig.l 1 thus causing the actuating member 22 to engage the switch button 9 and force it to `the dottedy position shown in Fig. 1 thus breaking the circuit to the motor and stopping the pump. This is a safety device vfor preventing flooding of the furnace with oil 95 if the oil failsy to ignite. Supported on the wall of the furnace isa casing 24 into which a gas pipe 25 leads andthe gas pipe is provided with a jet 26 'of porcelain, clay or lava to prevent deterioration and this jet throws a flame toward the oiland air jet 10 for igniting the oilfwhen it' begins to flow from the jet 10. A relightingplug 27 is provided in the Side of" the casing 24 whichy may be removed for re-lighting the gas pilot,I should it ever go out. An air inlet opening 28 which is open to atmosphere is provided in the side of the casing 2d opposite the plug 27 and a bracket 29 is secured to the casing 24 and supports a bulb 30 in the air inlet opening 28. This bulb 30 is connected by means ot a tube 31 with the interior of a vertically expandible element 32 having a plunger 33 at the upper end thereof extending through an opening provided therefor' in the stationary bracket 18. The upper` end of the plunger 33 normally lies flush with the surface of the bracket 18. rllhe expandible element 32, tube 31 and bulb 30 are filled with a volatile Huid such as ether which is quickly expandible under influence ot heat. The gaspilot which remains lighted all the time draws air to support combustion through the air inlet 28 and thus maintains the bulb 30 in a cool condition. The switch 8 normally remains in the closed position as shown in Fig. 1 during normal operation ot the furnace and is only moved to the oilc position by the actuator 22 wheat-he oil tails to ignite. lilith the switch 8 closed or on the on position the device vis ready for operation. Assuming that the switch 7 shown in Fig. 2 is closed by a thermostat the motor 4 is driven and drives the pump 1 which .feeds air under pressure through the pipe line 3 and through the jet 10. Ait the same time the air under pressure passes through the pipe 12 and very slowly through the small aperture in the member 14C to fill the er;- pandible element 15. At the same time the gas llame tromv the jet 26 ignites the oil passing from the jet which produces a puff at the instant ot ignition tending to blow the heat produced by the pilot or the flame ituelt backward through the chamber and air inlet4 28 and about the bulb 30. This pull immediately expands the volatile fluid in the bulb and member 32 forcing the plunger 33 upwardly and moving the link coni' 'ngrot the parts 20 and 21 tothe positon shown in dotted lines in Fig. 1 which prevents the actuator 22 from eugaging the switch button 9 and allows the furnace to operate in the normal manner. lillhen the thermostat again opens the switch 7 the pump is stopped which reduces the pressure in the cxpandiblo element and allows the spring 19 to move the plunger 16 to the right o'l" Fig. 1 until the links and 21 are turned to the position shown in full lines in Fig. 1 and straightened out at which time the device is again ready for succeeding operations. In case the oil does notignitefno puit of llame is produced about the bulb and therefore the' plunger 33 does not move the links out ot 'alignment and-as the `pressure is built up'in the expandible element 15 the actuator 22 is moved to the lett of Fig. 1 thus moving the switch button 9 to the dotted position and opening the switch 8 to break the motor circuit and stop the motor and pump thus preventing further fuel from passing into the Jfurnace. lllhen this has happened and the parts are returned to the normal position shown in full lines in Fig. 1 the operator pushes the button 9 to the position shown in full lines in Fig. 1 at which time the burner is again ready for operation.

In the lconstruction of the device herein described an air pressure ot approximately four pounds was provided discharging through the pipe 12 Vand the restricted oritice 14 was formed by a No. 8O drill. The plunger .17 has a movement of' about threesixteenths ol an inch to engage the switch button 9 while the plunger has a Inovement of about three thirty-secondsot an inch to break the toggle formed by the links 20 and 21. The size of the bellows member 15 is such that the air pressure multiplied by the cross sectional area. is in excess oitl the presuro required to operate the push button 9. rlhe size ot the bellows 32, the conduit7 31 or pump 30, is notmaterial but only a` small quantity ot ether should be employed in the bulb as too great a volume would produce too great a pressure and the pressure required to operate the plunger 33 is only that required to litt the links of the toggle which are simply two small brass bars. rEhe size oi" the orifice/28 in the pilot flame casing needs to be sutlieiently great to permit tree low or gases about the bulb 3Q which is thin walled in order to permit rapid transfer of heat to the ether. The pilot flame should be merely of medium size, too large size flame usually being too great in pressure and therefore tending to prevent the blow back77 upon ignition of the oil in theturnace and too small a pilot llame tending to blow out. This lamemaybe regulated by a valve not here shown in the conduit 25 to secure the desired result. With a medium flame theA pressure developed upon ignition tends to cause an instantaneous dicker of the flame to about the -bulb and then a return to the position shown in the drawing.

lt is to be understood, however, that the invention is not restricted to the specific,`

sizes given as the only materialiv important 'factor is to provide a pressure in the bellows 15 suflioient in. respect to its cross sectional area to exceed the pressure required to ac tuate the switch button and that this pressure shall build up slowly through a sollicient time period subsequent to operation ot the electrically controlled means to perf mit ignition to take place as hereinbefore Y describec u 4 From the foregoing description it becomes evident that the device is very simple and efficient in operation, will not easily get out of order, will preventflooding of the furnace with oil and provides a device which accomplishes the objects described.

Having thus fully described my invention, its utility and mode of operation, what l claim and desire to secure by Letters Patent of the United States is l. The combination with a furnace, of a fuel oil burner having a fuel nozzle discharging into the' furnace, electrically controlled means for discharging oil through the saidnoz'zle, a switch in the circuit for the said electrically controlled means, a pressure actuated device caused to operate upon operation of the electrically controlled means to discharge the oil into the furnace, the said pressure actuated -device being v arranged to open the switch at a certain time period subsequent to discharge of oil into the furnace, a conduit open to the furnace, a pilot flame extending thii'ough the conduit and adapted to ignite the oil when discharged, a device sensitive to change in temperature positioned adjacent the pilot flame and when heated to a predetermined extent adapted to prevent switch actuation by the pressure actuated device, the arrangement providing that, upon normal operation of the device and ignition of the fuel by the pilot, the increase of pressure within the furnace at the time of ignition causes heat of the pilot llame to be forced backwardly through the conduit to influence the temperature sensitive device.

2. The combination with a furnace, of a fuel oil burner having a fuel nozzle discharging into the furnace, electrically controlled means for discharging Oil through the nozzle, a switch in the circuit for the said electrically controlled means, a pressure actuated device caused to operate upon operation of the electrically controlled means, the said pressure actuated means being arranged to open the switch at a certain time period subsequent to discharge of oil into the furnace, a pilot flame adapted to ignite the oil being discharged from the nozzle, a. conduit for the pilot flame open to air eX- teriorly of the furnace, the air normally flowing into the furnace through the conduit to supply oxygen to the pilot flame, a temperature sensitive device supported 1n the air inlet end of the said conduit and adapted upon application of heat to prevent actuation of the switch by the pressure actuated means, the arrangement being such that upon ignition of the oil heat is applied to the said temperature sensitive means.

3. An automatic cut off device for fuel oil burners comprising a furnace, an oil nozzle.

opening into the furnace, means for supplying air under pressure to the nozzle, a pilot light adapted to light the oil as it discharges from the nozzle, an air inlet through which air is adapted to be drawn to supply the pilot light, an expandible element having a bulb supported in the air inlet opening, the expandible element and bulb being filled with a volatile fluid, a second expandible element adapted to be slowly filledwith the air under pressure, expansion Lof the said element by the air under pressure being adapted to actuate a switch, the arrangement being such that upon ignition of the oil the first named eXpandible element prevents the second element from actuating the switch. 'i

4:. An automatic cut-olf device for fuel oil burners comprising the combination with a furnace, of an oil nozzle discharging into the furnace, means for supplying air to the nozzle to cause discharge of oil, an eX- pandible element connected directly with the air supplying means and movable through the airy pressure, electrical means for providing the air supply, a switch controlling the circuit therefor, said switch being positioned to be operated by the eX- pandible element to break the circuit to the electrically controlled means, a temperature sensitive means to which heat is arranged to be supplied by pressure developed through ignition of the fuel supply, and means actuated by the temperature sensitive device to prevent operation of the switch by the expandible member.

5. An automatic cut-off device for fuel oil burners comprising the combination with a furnace, of a nozzle for discharging oil thereinto, an air pump for forcing air and oil under pressure through the nozzle, an electric motor foi` driving the pump, a circuit for the motor including a switch for making and breaking the same, an expandible element consisting of a bellows member having a stem movable by expansion or contraction of the bellows member, said stem including a jointed portion intermediate its ends, said switch being located in alignment with the stem whereby on expansion of the element and engagement of the stem with the switch the circuit is broken, and means influenced, through ignition of the fuel in the furnace to move the `jointed portion out of alignment with the remaining portions of the stem thereby permitting expansion of the bellows member without causing operation of the switch.

rAn automatic cut-off device for fuelr oil burners comprising electrically controlled means for discharging oil and air into the furnace, a circuit for the said means, a switch in the circuit, anexpandible element actuated by air pressure and operating in a predetermined time period to operate the switch and break the circuit, a pilot flame for ignition of the fuel including an enclosing casing having an opening to atmosphere and a conduit leading into the lll() furnace in proximity to the fuel injected element under influence of heat to prevent thereinto, a temperature sensitive element at operation of the switch by the pressure aotlie opening to atmosphere, the parts being tuated device. 10 so arranged that pressure developed in the In testimony whereof I Sign this specificafurnace on ignition of the fuel causes the tion.

pilot iame to blow back to the said opening to Contact Wit-l1 the temperature sensitive DORR R. MARTIN. 

